The scientists also agreed that physical activity is an important part of staying healthy.

Their report suggests that people should undertake at least one hour of physical activity of moderate intensity each day.

Dr Ricardo Uauy, chairman of the WHO expert group and professor of public health nutrition at the London School of Hygiene and Tropical Medicine, said improving eating habits would improve health.

"People should eat less high-calorie foods, especially foods high in saturated fat and sugar, be physically active, prefer unsaturated for saturated fat and use less salt; enjoy fruits, vegetables and legumes and prefer foods of plant and marine origin."

Billion overweight

More than a billion people worldwide are now overweight, of whom at least 300 million are clinically obese, according to WHO.

In the UK, the number of men considered obese has more than doubled from 8% in the 1980s to 17% now, while the rate for women has soared from 9% to 21%.

The situation is mirrored among children with nearly one in five youngsters in England overweight.

Tim Lang, professor of food policy at the City University, London, backed the report.

"Probably the single fastest way to reduce strokes in this country is to halve the amount of salt that's added to processed food.

"We also need to teach people basic cooking skills so they can turn fresh fruit and vegetables into things they want to eat."